Cell therapy methods have been developed in order to enhance the host immune response to tumors, viruses and bacterial pathogens. Cell therapy methods often involve the ex-vivo activation and expansion of T-cells. Examples of these type of treatments include the use tumor infiltrating lymphocyte (TIL) cells (see U.S. Pat. No. 5,126,132 issued to Rosenberg), cytotoxic T-cells (see U.S. Pat. No. 6,255,073 issued to Cai, et al.; and U.S. Pat. No. 5,846,827 issued to Celis, et al.), expanded tumor draining lymph node cells (see U.S. Pat. No. 6,251,385 issued to Terman), and various other lymphocyte preparations (see U.S. Pat. No. 6,194,207 issued to Bell, et al.; U.S. Pat. No. 5,443,983 issued to Ochoa, et al.; U.S. Pat. No. 6,040,177 issued to Riddell, et al.; U.S. Pat. No. 5,766,920 issued to Babbitt, et al.).
For maximum effectiveness of T-cells in cell therapy protocols, the ex vivo activated T-cell population should be in a state that can maximally orchestrate an immune response to cancer, infectious diseases, or other disease states. For an effective T-cell response, the T-cells first must be activated. For activation, at least two signals are required to be delivered to the T-cells. The first signal is normally delivered through the T-cell receptor (TCR) on the T-cell surface. The TCR first signal is normally triggered upon interaction of the TCR with peptide antigens expressed in conjunction with an MHC complex on the surface of an antigen-presenting cell (APC). The second signal is normally delivered through co-stimulatory receptors on the surface of T-cells. Co-stimulatory receptors are generally triggered by corresponding ligands or cytokines expressed on the surface of APCs.
Due to the difficulty in maintaining large numbers of natural APC in cultures of T-cells being prepared for use in cell therapy protocols, alternative methods have been sought for ex-vivo activation of T-cells. One method is to by-pass the need for the peptide-MHC complex on natural APCs by instead stimulating the TCR (first signal) with polyclonal activators, such as immobilized or cross-linked anti-CD3 or anti-CD2 monoclonal antibodies (mAbs) or superantigens. The most investigated co-stimulatory agent (second signal) used in conjunction with anti-CD3 or anti-CD2 mAbs has been the use of immobilized or soluble anti-CD28 mAbs.
The combination of anti-CD3 mAb (first signal) and anti-CD28 mAb (second signal) immobilized on a solid support such as paramagnetic beads (see U.S. Pat. No. 6,352,694 issued to June, et al.) has been used to substitute for natural APCs in inducing ex-vivo T-cell activation in cell therapy protocols (Levine, Bernstein et al. 1997; Garlie, LeFever et al. 1999; Shibuya, Wei et al. 2000). While these methods are capable of achieving therapeutically useful T cell populations, the use of paramagnetic beads makes the ease of preparation of T-cells less than ideal. Problems include the high cost of the beads, the labor-intensive process for removing the beads prior to cell infusion, and the inability of the beads to activate CD8 T-cell subsets (Deeths, Kedl et al. 1999; Laux, Khoshnan et al. 2000). In addition, the T-cell populations resulting from this method, and other prior art T-cell stimulation methods, lack the type of robustness required for eliciting effective immune stimulation when infused into patients. As a consequence, no prior art cell therapy protocols have demonstrated significant efficacy in clinical settings.
This has motivated the search for more effective methods for activating T-cells for use in cell therapy protocols. One such method is the use of APC tumor cell lines that have been genetically modified to express receptors that bind mAbs. These modified APC can be loaded with anti-CD3 and anti-CD28 mAbs (Thomas, Maus et al. 2002) or additionally modified to express the ligand for 4-1BB (Maus, Thomas et al. 2002) and then used to activate T-cells for use in cell therapy protocols. It was found that these modified APCs resulted in more effective activation of T-cell populations than the use of CD3/CD28-coated paramagnetic beads. However, the use of genetically-manipulated tumor cell lines in cell therapy protocols raises safety concerns which limit the commercial application of this technique.